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What is torque? How do we calculate torque?. Key Questions:. Performance Objectives. Measure forces and distances in a simple machine. Calculate torque. Apply the concept of mechanical advantage to levers. Build three classes of levers. Lever Assembly. SAFETY NOTE:
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What is torque? How do we calculate torque? Key Questions:
Performance Objectives • Measure forces and distances in a simple machine. • Calculate torque. • Apply the concept of mechanical advantage to levers. • Build three classes of levers.
Lever Assembly • SAFETY NOTE: • WATCH for FALLING weights on bare toes or sandals or table tops! • DO not place the fulcrum higher than hole 3 of stand!
Torque • Levers use torque to lift or move objects. • Torque is a force applied over a distance that causes ROTATION to occur. • Torque is measured in Newtonmeters (Nm)
Force x Distance = Force x Distance Review of levers Input Force x Length of Input Arm Output Force x Length of Output Arm = = Torque Force X Distance
An Example of Torque • Calculate the torque created when opening the door.
Torque and direction • If more than one torque acts on an object, the torques are combined to determine the net torque. • If the torques tend to make an object spin in the same direction (clockwise or counterclockwise), they are added together. • If the torques tend to make the object spin in opposite directions, the torques are subtracted. • Torques causing counterclockwise rotation are positive and torques causing clockwise rotation are negative.
The variables in a simple machine can be adjusted make work easier or resist forces on purpose. Consider two levers: Forces and Machines
The advantage the simple machine gives to the user can be calculated. A machine approaches a mechanical advantage of 1, when output forces roughly equal input forces. Forces and Machines
Mechanical Advantage Output force (N) MA = Fo Fi mechanical advantage Input force (N)
Mechanical advantage • What is the mechanical advantage of this new lever?
Torque and mechanical advantage • What’s the mathematical relationship between torque and mechanical advantage? • MA = Output Torque ÷ Input Torque
Three Classes of Levers • First Class - fulcrum between Input and output • Second Class – output between fulcrum and input • Third Class – input between fulcrum and output
Levers and the human body • Your body contains muscles attached to bones in ways that act as levers. • Here the biceps muscle attached in front of the elbow opposes the muscles in the forearm. Can you think of other muscle levers in your body?
Mobiles are levers! • GREAT STEM project!
Outcomes • Usescience • Thinkscientifically • Communicatetechnical ideas • Teachall students • Be science conscious NOT science phobic
What questions do you have about Torque or Mechanical Advantage?